1. Field of the Invention
The present invention relates to a control system for a prime mover and a hydraulic pump of a hydraulic construction machine, and more particularly to an auto-acceleration system for a prime mover of a hydraulic construction machine, such as a hydraulic excavator, wherein hydraulic actuators are operated by a hydraulic fluid delivered from a hydraulic pump, which is driven by an engine for rotation, for carrying out works required.
2. Description of the Prior Art
Generally, in the hydraulic construction machine such as a hydraulic excavator, a diesel engine is provided as a prime mover, at least one variable displacement hydraulic pump is driven by the diesel engine for rotation, and a plurality of hydraulic actuators are operated by a hydraulic fluid delivered from the hydraulic pump for carrying out works required. The diesel engine is provided with input means, such as an accelerator lever, for instructing a target revolution speed. An amount of fuel injected is controlled depending on the target revolution speed, and an engine revolution speed is controlled correspondingly.
For control of the prime mover and the hydraulic pump in such hydraulic construction machine, a control system is proposed in JP, A, 7-119506 entitled "Revolution Speed Control System for Prime Mover of Hydraulic Construction Machine". In the disclosed control system, a target revolution speed is input, as a reference, by operating a fuel lever, and the direction and input amount in and by which control levers or pedals of operation instructing means respectively associated with a plurality of hydraulic actuators are each operated (hereinafter referred to simply as the lever operating direction and lever input amount), as well as an actuator load (pump delivery pressure) are detected. A modification value of the engine revolution speed is determined based on the lever operating direction, the lever input amount and the actuator load, and the target revolution speed is modified using the revolution speed modification value to thereby control the engine revolution speed. In this control system, when the lever input amount is small and when the actuator load is low, the engine target revolution speed is set to a relatively low value for energy saving. When the lever input amount is large and when the actuator load is high, the engine target revolution speed is set to a relatively high value for increasing working efficiency.